Flexible display device

ABSTRACT

A display device includes: a flexible substrate; a pixel over the flexible substrate, the pixel including a transistor and a display element; a first wiring for transmitting a signal to the pixel, the first wiring extending in a first direction; a second wiring extending in a second direction intersecting the first direction; an inorganic insulating layer on a higher level than the first wiring or the second wiring; and an organic insulating layer on a higher level than the inorganic insulating layer, wherein the inorganic insulating layer has an opening exposing a part of the upper surface of the first wiring or the second wiring is exposed, and the organic insulating layer is provided in such a way as to fill the opening.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/373,533 filed Dec. 9, 2016. Further, this application claims thebenefit of priority from the prior Japanese Patent Application No.2015-248687, filed on Dec. 21, 2015, and the prior Japanese PatentApplication No. 2016-020546, filed on Feb. 5, 2016, the entire contentsof which are incorporated herein by reference.

FIELD

The present invention relates to display devices, and an embodiment ofthe invention disclosed herein relates to a configuration of aninterlayer insulating layer that is provided in a flexible displaydevice.

BACKGROUND

Instead of a flat-plate display device that is fabricated using a hardglass substrate, a sheet-like display device using a flexible substratesuch as a plastic film (such a display device being also referred to as“sheet display”) is currently under development. Since the sheet displayis light in weight, hard to be broken, and capable of being folded orbent into a curved surface, it is expected to be developed for newapplications.

In a display unit of the display device, pixels arranged in a matrix aredriven by pixel circuits that are formed by thin-film transistors. Eachof the thin-film transistors includes a semiconductor film, a gateinsulating film, and a gate electrode, and each of the pixel circuits isformed by a scanning signal line, a video signal line, and the like thatare provided via an interlayer insulating layer.

However, bending the flexible substrate cracks the gate insulating filmand the interlayer insulating film, each of which is made of aninorganic insulating material over substantially the entire surface ofthe display unit, thus undesirably affecting the reliability of thedisplay device. To address such a problem, Japanese Unexamined PatentApplication Publication No. 2007-288078 discloses a structure in which,by removing those portions of a laminate of insulating films (i.e. alaminate including a gate insulating film and an interlayer insulatingfilm) which are present in regions where no thin-film transistors areformed, this insulating film laminate is separated into islands.

Incidentally, a resin substrate that is used as the flexible substrateis higher in moisture permeability and moisture absorbency than a glasssubstrate and, as such, requires a barrier film constituted by a siliconnitride film or the like. In the display device disclosed in JapaneseUnexamined Patent Application Publication No. 2007-288078, even thoseportions of the insulating films which are provided on foundationsurfaces of the thin-film transistors are removed, with the result thatmoisture diffuses into the display device. Having diffused into thedisplay device, the moisture causes deterioration not only in thethin-film transistors but also in display elements that are formed usingliquid crystals and an organic electroluminescence material. Therefore,the display device disclosed in Japanese Unexamined Patent ApplicationPublication No. 2007-288078 can be made higher in resistance to thebending of the flexible substrate but becomes lower in reliability dueto the deterioration in the display elements caused by the moisture orthe like.

SUMMARY

An embodiment of the present invention provides a display deviceincluding: a flexible substrate; a pixel over the flexible substrate,the pixel including a transistor and a display element; a first wiringfor transmitting a signal to the pixel, the first wiring extending in afirst direction; a second wiring extending in a second directionintersecting the first direction; an inorganic insulating layer on ahigher level than the first wiring or the second wiring; and an organicinsulating layer on a higher level than the inorganic insulating layer,wherein the inorganic insulating layer has an opening exposing a part ofthe upper surface of the first wiring or the second wiring is exposed,and the organic insulating layer is provided in such a way as to fillthe opening.

An embodiment of the present invention provides a display deviceincluding a pixel unit, the pixel unit including: a plurality of pixelsarranged in a first direction and a second direction intersecting thefirst direction; first wirings for transmitting signals to the pluralityof pixels arranged in the first direction, the first wirings extendingalong the first direction; second wirings for transmitting signals tothe plurality of pixels arranged along the second direction intersectingthe first direction, the second wirings extending in the seconddirection intersecting the first direction; and an inorganic insulatinglayer covering at least either the first wirings or the second wirings,wherein the inorganic insulating layer has openings exposing at leasteither the first wirings or the second wirings, and the openings areprovided along at least either the first direction or the seconddirection intersecting the first direction.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing the appearance of a display deviceaccording to an embodiment of the present invention;

FIG. 2 is a diagram showing a configuration of the display deviceaccording to the embodiment of the present invention;

FIG. 3 is a diagram showing an equivalent circuit of a pixel of thedisplay device according to the embodiment of the present invention;

FIG. 4 is a plan view showing a layout of the pixel of the displaydevice according to the embodiment of the present invention;

FIG. 5 is a plan view showing a configuration of a pixel unit of thedisplay device according to the embodiment of the present invention;

FIG. 6 is a cross-sectional view showing a structure of the pixel unitof the display device according to the embodiment of the presentinvention;

FIG. 7 is a cross-sectional view showing a structure of the pixel unitof the display device according to the embodiment of the presentinvention;

FIG. 8 is a plan view showing a configuration of a pixel unit of adisplay device according to an embodiment of the present invention;

FIG. 9 is a cross-sectional view showing a structure of the pixel unitof the display device according to the embodiment of the presentinvention;

FIG. 10 is a plan view showing a configuration of a pixel unit of adisplay device according to an embodiment of the present invention;

FIG. 11 is a cross-sectional view showing a structure of the pixel unitof the display device according to the embodiment of the presentinvention;

FIG. 12 is a plan view showing a configuration of a pixel unit of adisplay device according to an embodiment of the present invention;

FIG. 13 is a cross-sectional view showing a structure of the pixel unitof the display device according to the embodiment of the presentinvention;

FIG. 14 is a plan view showing a layout of a pixel of a display deviceaccording to an embodiment of the present invention;

FIG. 15 is a plan view showing a configuration of a pixel unit of thedisplay device according to the embodiment of the present invention;

FIG. 16 is a cross-sectional view showing a structure of the pixel unitof the display device according to the embodiment of the presentinvention;

FIG. 17 is a cross-sectional view showing a structure of the pixel unitof the display device according to the embodiment of the presentinvention;

FIG. 18 is a cross-sectional view showing a structure of a pixel unit ofa display device according to an embodiment of the present invention;

FIG. 19 is a plan view showing a configuration of a pixel unit of adisplay device according to an embodiment of the present invention;

FIG. 20 is a cross-sectional view showing a structure of the pixel unitof the display device according to the embodiment of the presentinvention;

FIG. 21 is a cross-sectional view showing a structure of the pixel unitof the display device according to the embodiment of the presentinvention;

FIG. 22 is a perspective view showing the appearance of the displaydevice according to the embodiment of the present invention;

FIG. 23 is a cross-sectional view showing a structure of the pixel unitof the display device according to the embodiment of the presentinvention;

FIG. 24 is a cross-sectional view showing a configuration of a pixelunit of a display device according to an embodiment of the presentinvention;

FIG. 25 is a plan view showing a configuration of a pixel unit of adisplay device according to an embodiment of the present invention;

FIG. 26 is a cross-sectional view showing a structure of the pixel unitof the display device according to the embodiment of the presentinvention; and

FIG. 27 is a plan view showing a configuration of a pixel unit of adisplay device according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention are described below with referenceto the drawings and the like. Note, however, that the present inventionmay be carried out in many different aspects and should not be narrowlyinterpreted within the limits of the contents of description of theembodiments illustrated below. For a clearer description, the drawingsmay schematically show the width, thickness, shape, and the like of eachcomponent in comparison with actual aspects; however, they are mereexamples and, as such, are not intended to limit the interpretation ofthe present invention. Further, in the present specification and each ofthe drawings, elements that are identical to those previously describedwith reference to a preceding drawing are given the same referencenumerals, and a detailed description of such elements may be omitted asappropriate. Reference numerals each with a letter such as “a” or “b”added to the end of a number may be used for distinguishing identicalelements. Furthermore, a word “first” or “second” added to the beginningof an element is a convenient mark that is used for identifying theelement, and means nothing more than that unless otherwise noted.

In the present specification, unless otherwise noted, cases where amember or region is located “over (or under)” another member or regionencompass not only cases where a member or region is located immediatelyabove (or immediately below) another member or region but also caseswhere a member or region is located above (or below) another member orregion, i.e. cases where another constituent element is inserted above(or below) another member or region.

In the present specification, a display device includes a firstsubstrate. The first substrate has at least one planar principal surfaceover which a plurality of thin films are provided to form a layeredstructure. The following description bases a cross-sectional view on theprincipal surface of the first substrate and refers to the upper side ofthe principal surface as “over”, “higher level”, or “above”.

Outline of Display Device

FIG. 1 is a perspective view of a display device 100 according to anembodiment of the present invention. The display device 100 includes apixel unit 106 in which a plurality of pixels 116 are arranged, and thispixel unit 106 forms a display screen. The pixels 116 are formed on afirst substrate 102. The first substrate 102 is a flexible substrate.For example, the first substrate 102 is a sheeted organic resin film.Further, the pixel unit 106 provided on the first substrate 102 iscovered with a second substrate 104. The second substrate 104 is asealing member, and as with the first substrate 102, the secondsubstrate 104 may be a sheeted member. Alternatively, a coating of resinmaterial may be provided as a sealing member that corresponds to thesecond substrate 104.

In a case where the pixel unit 106 is provided on the first substrate102, the display device 100 has two possibilities: the display screen isviewed from either the second substrate 104 side or the first substrate102 side. It is assumed that the display device 100 shown in FIG. 1 isconfigured such that the display screen that is formed by the pixel unit106 is viewed from the second substrate 104 side.

With the flexibility of the first substrate 102, the display device 100enables the display screen to be bent in at least one direction. FIG. 1shows an example of a state where the display device 100 is bent in afirst direction (i.e. an X direction shown in FIG. 1). The displaydevice 100 is bent so that the display screen forms a convex surface. Itshould be noted that although FIG. 1 shows an example where the displaydevice 100 bends in the X direction, the present invention is notlimited to this example. The display device 100 is also bendable in asecond direction (i.e. a Y direction shown in FIG. 1) intersecting thefirst direction and, furthermore, is bendable in both the X and Ydirections. Further, the display device 100 is configured to be alsobendable in an oblique direction with respect to the X and Y directions.In addition to allowing the display screen to be bent into a convexsurface, the display device 100 is configured to also enable the displayscreen to be bent into a concave surface.

FIG. 2 shows a circuit configuration of such a display device 100. Thedisplay device 100 includes the pixel unit 106, in which the pixels 116are arranged, a first drive circuit 108, a second drive circuit 110, athird drive circuit 112, and a terminal unit 114 including a pluralityof terminals 118. Each of these components is provided over the flexiblefirst substrate 102. The embodiment of the present invention assumesthat the pixels 116 are provided with light-emitting elements as displayelements. It should be noted that the display elements are not limitedto the light-emitting elements but may be other types of elements thatare used for displaying images. For example, the display elements may beliquid crystal elements based on the electrooptic effect of liquidcrystals or electrochromic elements.

The pixel unit 106 includes first gate wirings 120, second gate wirings122, and data wirings 124. The first gate wirings 120 and the secondgate wirings 122 extend in a row-wise direction (i.e. an X directionshown in FIG. 2), and the data wirings 124 extend in a column-wisedirection (i.e. a Y direction shown in FIG. 2). Further, the pixel unit106 includes first power source lines 126 via which electric power issupplied to the light-emitting elements of the pixels 116. The firstdrive circuit 108 outputs signals to the first gate wirings 120. Thesecond drive circuit 110 outputs signals to the second gate wirings 122.The third drive circuit 112 outputs signals to the data wirings 124. Theterminal unit 114 receives signals that drive the display device 100.

It should be noted that although FIG. 2 shows an example where thepixels 116 are squarely arranged in rows and columns, the embodiment ofthe present invention is not limited to this example. For example, thepixels 116 may be arranged in another arrangement such as a deltaarrangement or a Pen Tile arrangement. Further, such components of thedisplay device 100 as the driving circuits, the signal lines, and thepower source lines may be modified as appropriate.

FIG. 3 shows an example of a circuit configuration (pixel circuit) ofeach of the pixels 116. The pixel circuit includes a first transistor130, a second transistor 132, a drive transistor 134, a light-emittingelement 136, and a retentive capacitive element 138. The drivetransistor 134 includes the following terminals: a gate that serves as acontrol terminal and a source and a drain that serve as input and outputterminals. For example, in FIG. 3, the drain of the drive transistor 134is electrically connected to the corresponding one of the first powersource lines 126 via the second transistor 132, and the source of thedrive transistor 134 is electrically connected to a first terminal ofthe light-emitting element 136. The light-emitting element 136 has itsfirst terminal connected to the first power source line 126 via thedrive transistor 134 and the second transistor 132 and its secondterminal connected to the corresponding second power source line 128.The first power source line 126 is supplied with a high potential(PVDD), and the second power source line 128 is supplied with a lowpotential (PVSS).

The gate of the drive transistor 134 is electrically connected to thecorresponding one of the data wirings 124 via the first transistor 130.The operation of turning on and turning off the first transistor 130 iscontrolled in accordance with a control signal SG (having amplitudeVGH/VGL) that is supplied to the corresponding one of the first gatewirings 120. The first transistor 130 is controlled to be on by ahigh-potential control signal VGH and controlled to be off by alow-potential control signal VGL. When the first transistor 130 is on,an electric potential based on a data signal from the data wiring 124 issupplied to the gate of the drive transistor 134. Similarly, theoperation of turning on and turning off the second transistor 132 iscontrolled in accordance with a control signal BG (having amplitudeVGH/VGL) that is supplied to the corresponding one of the second gatewirings 122.

The retentive capacitive element 138 is provided between the source andgate of the drive transistor 134. The retentive capacitive element 138retains a gate voltage of the drive transistor 134. The emissionintensity of the light-emitting element 136 is controlled by a draincurrent of the drive transistor 134. The electric potential based on thedata signal is supplied to the gate of the drive transistor 134, andwhen the second transistor 132 is turned on, an electric current flow tothe light-emitting element 136. This causes the light-emitting element136 to emit light.

FIG. 4 shows an arrangement of the first transistor 130, the secondtransistor 132, the drive transistor 134, the light-emitting element136, the retentive capacitive element 138, the first gate wiring 120,the second gate wiring 122, the data wiring 124, and the first powersource line 126 in the pixel 116.

The drive transistor 134 includes a semiconductor layer 142 a and a gateelectrode 148 a. The semiconductor layer 142 a has a source regionconnected to a source wiring 154 through a first contact hole 166 a anda drain region connected to a drain wiring 156 through a second contacthole 166 b. The source wiring 154 is connected to a pixel electrode 162through a third contact hole 166 c. The first transistor 130 includes asemiconductor layer 142 b and a gate electrode 148 b, and the gateelectrode 148 b is connected to a first gate wiring 120 a extending in afirst direction (i.e. an X direction shown in FIG. 4). One of the inputand output terminals, which correspond to the source and the drain, ofthe first transistor 130 is connected to a data wiring 124 a extendingin a second direction (i.e. a Y direction shown in FIG. 4) intersectingthe first direction, and the other of the input and output terminals isconnected to a gate wiring 150 connected to the gate electrode 148 a ofthe drive transistor 134. The second transistor 132 includes asemiconductor layer 142 c and a gate electrode 148 c, and the gateelectrode 148 c is connected to a second gate wiring 122 a extending inthe first direction (i.e. the X direction shown in FIG. 4). One of theinput and output terminals, which correspond to the source and thedrain, of the second transistor 132 is connected to a first power sourceline 126 a extending in the second direction (i.e. the Y direction shownin FIG. 4) intersecting the first direction, and the other of the inputand output terminals is connected to the drain wiring 156 connected tothe drain of the drive transistor 134. The retentive capacitive element138 is formed in a region where the semiconductor layer 142 a overlaps aretentive capacitive electrode 164. It should be noted that FIG. 4 omitsto illustrate the gate insulating layer, the interlayer insulatinglayer, or the like.

As shown in FIG. 1, the display device 100 according to the embodimentof the present invention enables a region including the display screento be bent. Moreover, the display device 100 includes a structure thatprevents a decrease in reliability even in a case where the pixel unit106 is bent. The structure is described in detail below.

First Embodiment

The present embodiment exemplifies a structure of a display device thatis bendable in at least one direction. FIG. 5 shows an aspect in whichpixels 116 configured as shown in FIG. 4 are arranged in the pixel unit106. FIG. 5 shows a first pixel 116 a, a second pixel 116 b, a thirdpixel 116 c, a fourth pixel 116 d, first gate wirings 120 a, 120 b, and120 c extending in a first direction (i.e. an X direction shown in FIG.5), second gate wirings 122 a, 122 b, and 122 c extending in the firstdirection, data wirings 124 a, 124 b, and 124 c extending in a seconddirection (i.e. a Y direction shown in FIG. 5) intersecting the firstdirection, and first power source lines 126 a, 126 d, and 126 cextending in the second direction. That is, in the pixel unit 106, thefirst gate wirings 120 and the second gate wirings 122 extend along thedirection in which the first pixel 116 a and the fourth pixel 116 d arearranged, and the data wirings 124 and the first power source lines 126extend in the direction in which the first pixel 116 a and the secondpixel 116 b are arranged.

Although not clearly shown in FIG. 5, a first insulating layer made ofan inorganic insulating material is provided between the first gatewirings 120 a and 120 b and the data wirings 124 a and 124 b, betweenthe first gate wirings 120 a and 120 b and the first power source lines126 a and 126 b, between the second gate wirings 122 a and 122 b and thedata wirings 124 a and 124 b, and between the second gate wirings 122 aand 122 b and the first power source lines 126 a and 126 b. Moreover,the first insulating layer is provided with first openings 176 a to 176f through which parts of the upper surfaces of the first gate wirings120 a, 120 b, and 120 c are exposed. Further, the first insulating layeris provided with second openings 178 a to 178 f through which parts ofthe upper surfaces of the second gate wirings 122 a, 122 b, and 122 care exposed.

Next, FIG. 6 shows a cross-sectional structure taken along line A-B inFIG. 5. It should be noted that this line A-B corresponds to line A-B inthe layout drawing of the pixel 116 shown in FIG. 4.

FIG. 6 shows cross-sectional structures of the drive transistor 134, thelight-emitting element 136, and the retentive capacitive element 138.Further, FIG. 6 shows a cross-sectional structure of the first gatewiring 120 a, the second gate wiring 122 d, the first power source line126 a, and the data wiring 124 b. These elements are provided over thefirst substrate 102.

It should be noted that the first substrate 102 is a flexible substrate.For example, the first substrate 102 is an organic resin film. A usableexample of the organic resin film is a polyimide film. It is preferablethat the polyimide film have a thickness of 1 to 100 μm, more preferably1 to 50 μm. Although polyimide is merely an example of a substratematerial, this material is superior in heat resistance, chemicalresistance, and mechanical strength and, as such, is suitable as asubstrate material for use in the present embodiment.

A foundation insulating layer 140 is provided on a first surface of thefirst substrate 102 on which the drive transistor 134 is provided. Inthe present embodiment, the foundation insulating layer 140 is not anessential component but functions as a barrier layer that preventsimpurities from diffusing from the first substrate 102 side to thesemiconductor layer 142 side.

The drive transistor 134 is constituted by the semiconductor layer 142a, a gate insulating layer 146, and the gate electrode 148 a. The sourceregion of the semiconductor layer 142 a is connected to the sourcewiring 154, and the drain region of the semiconductor layer 142 a isconnected to the drain wiring 156. A first insulating layer 152 isprovided between the gate electrode 148 a and the source wiring 154 andbetween the gate electrode 148 a and the drain wiring 156. The sourcewiring 154 is in contact with the source region of the semiconductorlayer 142 a via the first contact hole 166 a formed in the firstinsulating layer 152, and the drain wiring 156 is in contact with thedrain region of the semiconductor layer 142 a via the second contacthole 166 b formed in the first insulating layer 152.

A second insulating layer 158 is provided over the first insulatinglayer 152. A pixel electrode 162 is provided over the second insulatinglayer 158. The second insulating layer 158 serves as a foundationsurface for the pixel electrode 162 and is used as a planarization filmthat planarizes this foundation surface. The source wiring 154 and thepixel electrode 162 are connected to each other via the third contacthole 166 c formed in the second insulating layer 158.

In the present embodiment, each of the semiconductor layers 142 is madeof any of various semiconductor materials. For example, each of thesemiconductor layers 142 may be made of a silicon semiconductor or, morespecifically, made of a polycrystalline silicon film or an amorphoussilicon film. Alternatively, each of the semiconductor layers 142 may bemade of a metal oxide (e.g. also referred to as “oxide semiconductor”)having semiconducting properties. The gate electrode 148 a and the gatewiring 120 a are made of a metal material such as aluminum, titanium,molybdenum, or tungsten and, for example, have a structure in whichtitanium and aluminum are stacked. The first insulating layer 152 ismade of an inorganic insulating material and, for example, is a siliconnitride film or a laminate of a silicon nitride film and a silicon oxidefilm. The second insulating layer 158 is made of an organic insulatingmaterial and, for example, is made of a resin material such as polyimideor acrylic. Further, the foundation insulating layer 140 has a structurein which silicon oxide and silicon nitride are stacked and, for example,has a structure in which a silicon nitride film is sandwiched betweenupper and lower silicon oxide films.

The pixel electrode 162 has its outer edges surrounded by an insulatinglayer called a bank layer 168. The bank layer 168 covers the edges ofthe pixel electrode 162 and the third contact hole 166 c. Thelight-emitting element 136 is constituted by the pixel electrode 162, anorganic layer 170, and a counter electrode 172. The light-emittingelement 136 has a sealing layer 174 provided as the upper surfacethereof. The sealing layer 174 includes a silicon nitride film that isnot permeable to moisture or the like. Although not illustrated in FIG.6, the second substrate 104 is provided on a higher level than thesealing layer 174.

The organic layer 170 is constituted by one or more layers and at leastpartially contains an organic electroluminescence material. Thelight-emitting element 136 emits light when a voltage that is equal toor higher than an emission threshold voltage is applied between thepixel electrode 162 and the counter electrode 172. In the presentembodiment, the pixel electrode 162 is configured such that the lightemitted by the organic layer 170 is reflected by a laminate structure ofa transparent conductive film and a metal film. For example, the pixelelectrode 162 includes at least two transparent conductive films and ametal film (preferably made of a high-reflectance material such assilver (Ag) or aluminum (Al)) sandwiched between the two transparentconductive films. The counter electrode 172 is formed by a transparentconductive film. The light emitted by the organic layer 170 is emittedfrom the counter electrode 172 side.

The retentive capacitive element 138 has a structure in which the firstinsulating layer 152 and the source wiring 154 overlap the retentivecapacitive electrode 164. The retentive capacitive electrode 164 isformed by the same layer as the gate electrode 148 a.

In FIG. 6, the first insulating layer 152 is provided with a firstopening 176 a through which the upper surface of the first gate wiring120 a is exposed and a second opening 178 e through which the uppersurface of the second gate wiring 122 c is exposed. That is, the firstinsulating layer 152 has regions from which those portions of the firstinsulating layer 152 which overlap the parts of the upper surfaces ofthe gate wirings (first gate wiring 120 a, second gate wiring 122 c)have been removed. However, the first insulating layer 152 is providednot to expose all of the gate wirings (first gate wiring 120 a, secondgate wiring 122 c) located on a lower level than the first insulatinglayer 152 but to cover at least the side surfaces of the gate wirings(first gate wiring 120 a, second gate wiring 122 c).

Such first openings 176 and second openings 178 can be formed at thesame time as the first contact hole 166 a and the second contact hole166 b are formed in the first insulating layer 152. This eliminates theneed to increase the number of steps to form the first openings 176 andthe second openings 178 in the first insulating layer 152.

The first openings 176 and the second openings 178 each have a long,narrow opening shape along the direction in which the first gate wirings120 and the second gate wirings 122 extend. In other words, the firstinsulating layer 152 is provided with first openings 176 and secondopenings 178 that are rectangular in shape along one side of the pixelelectrode 162. Of course, the first openings 176 and the second openings178 are not provided in regions where the first gate wirings 120 and thesecond gate wirings 122 intersect the data wirings 124 and the firstpower source lines 126.

Since the first insulating layer 152 is made of an inorganic insulatingfilms such as a silicon oxide film or a silicon nitride film, it isbrittle. Therefore, bending the first substrate 102 to a certaincurvature or larger cracks the first insulating layer 152. Further, theprovision of the gate wirings causes stepped portions to be present on alower level than the first insulating layer 152. By being provided tocover these stepped portions, the first insulating layer 152 is placedin a situation where bending the first substrate 102 causes stress to beeasily concentrated on regions covering these stepped portions. That is,it can be said that stress is easily concentrated on those portions ofthe first insulating layer 152 which cover the first gate wirings 120and the second gate wirings 122 and that the first insulating layer 152is easily cracked by bending the first substrate 102. Meanwhile, sincethe first gate wirings 120 and the second gate wirings 122 are metalfilms, they have plasticity and have resistance to the bending of thefirst substrate 102.

The present embodiment prevents the occurrence of cracks by beingstructured to relax the bending stress on the first insulating layer 152by providing the first openings 176 and the second openings 178 inregions where the first insulating layer 152 overlaps the first gatewirings 120 and the second gate wirings 122. That is, by providingopenings (or notches) in regions in the first insulating layer 152 thatoverlap the gate wirings where stress is considered to be concentrated,the bending stress is prevented from being concentrated on a particularpart of the first insulating layer 152.

Furthermore, the first and second openings 176 and 178 provided in thefirst insulating layer 152 are filled with the organic insulatingmaterial forming the second insulating layer 158. By thus filling, withthe organic insulating material forming the second insulating layer 158,the regions from which the first insulating layer 152 has been removed,the first insulating layer 152 is prevented from being cracked when thefirst substrate 102 is bent.

By being structured such that the inorganic insulating layer coveringthe gate wirings are provided with the openings through which the uppersurfaces of the gate wirings are exposed and the openings are filledwith the organic insulating layer stacked on the inorganic insulatinglayer, the present embodiment allows this site to function as a stressrelaxation region. This site is hereinafter also referred to as “stressrelaxation region”. In a case where the display device 100 is bent asshown in FIG. 1, it is preferable that such a stress relaxation regionbe provided in the bent part.

In the present embodiment, by the openings (first openings 176, secondopenings 178) being provided in the first insulating layer 152 in such away as to extend in a direction along the gate wirings (first gatewirings 120, second gate wirings 122), a display device can be providedwhich is easily bent in a direction parallel to this direction by theaction of the stress relaxation region.

It should be noted that the first insulating layer 152 is used as aprotective film for the drive transistor 134 and the like. That is, thefirst insulating layer 152 functions as a blocking layer that preventsmoisture and the like from permeating the semiconductor layers 142.Nevertheless, since the first insulating layer 152 is provided with thefirst openings 176 and the second openings 178, there is concern thatthe function of the first insulating layer 152 as a blocking layer maybe impaired. However, the metal layer forming the gate wirings are ingeneral low in moisture vapor transmission rate and has the property ofpreventing permeation of moisture or the like. By providing the firstinsulating layer 152 with the first and second openings 176 and 178 overthe first and second gate wirings 120 and 122, respectively, the presentembodiment prevents the function of the first insulating layer 152 as ablocking layer from being impaired.

As a specific configuration, by the first insulating layer 152 includingat least one silicon nitride layer, the function of the first insulatinglayer 152 as a barrier layer that prevents permeation of impurities suchas moisture is enhanced. Further, the metal film of aluminum, titanium,molybdenum, or the like that is used as the first gate wirings 120 andthe second gate wirings 122 has barrier properties against moisture andthe like. For this reason, although the first insulating layer 152 isprovided with the first openings 176, the function of the firstinsulating layer 152 as a barrier layer can be maintained by providingthe first openings 176 so that the first openings 176 overlap the partsof the upper surfaces of the first gate wirings 120.

That is, a sealed structure that prevents permeation of impurities suchas moisture can be formed by setting the first openings 176 narrower inwidth than the first gate wirings 120 and covering the side surfaces andupper end faces of the first gate wirings 120 with the first insulatinglayer 152. This allows the semiconductor layer 142 a of the drivetransistor 134 to have its upper surface covered with the sealingstructure formed by the first insulating layer 152, the first gatewirings 120, and the second gate wirings 122 and its lower surfacecovered with the foundation insulating layer 140 including a siliconnitride film, thus making it possible to prevent permeation ofimpurities such as moisture and thereby prevent a decrease inreliability.

It should be noted that, as shown in FIG. 7, the first opening 176 a andthe second opening 178 e can be similarly provided also in a case wherea third insulating layer 160 formed by an inorganic insulating layer isprovided between the first insulating layer 152 and the secondinsulating layer 158. As with the first insulating layer 152, the thirdinsulating layer 160 is provided by a silicon oxide film, a siliconnitride film, or a laminate of a silicon nitride film and a siliconoxide film. In this case, the first insulating layer 152 and the secondinsulating layer 158 are stacked over the first gate wirings 120 and thesecond gate wirings 122, the first opening 176 a and the second opening178 e are provided in such a way as to penetrate these two insulatinglayers.

Thus, the present embodiment provides a display device that is easilybent in at least the direction in which the gate wirings extend.Moreover, since the first insulating layer can be prevented from beingcracked even when the display device is bent, a decrease in reliabilitycan be prevented.

Second Embodiment

The present embodiment shows examples of openings in the firstinsulating layer that are different from those shown in the firstembodiment. FIG. 8 shows an aspect in which such pixels 116 as thatshown in FIG. 4 are arranged in the pixel unit 106. Further, FIG. 9 is across-sectional view of a pixel as taken along line A-B in FIG. 8. Thefollowing description refers to FIG. 8 and FIG. 9. It should be notedthat this line A-B corresponds to line A-B in the layout drawing of thepixel 116 shown in FIG. 4. The following describes parts that aredifferent from those of the structure shown in FIG. 6.

In the present embodiment, the pixel unit 106 shown in FIG. 8 isprovided with the third insulating layer 160 on a higher level than thedata wirings 124 a, 124 b, and 124 c and the first power source lines126 a, 126 d, and 126 c. Moreover, the third insulating layer 160 isprovided with a third opening 180 a in a position that overlaps the datawiring 124 a, and is provided with a fourth opening 182 a in a positionthat overlaps the first power source line 126 a. The third opening 180 ais bored in the direction in which the data wiring 124 a extends, andthe fourth opening 182 a is bored in the direction in which the firstpower source line 126 a extends. The shapes of such openings are thesame as those of third openings 180 b and 180 c on the data wirings 124b and 124 c and those of fourth openings 182 c and 182 d on the firstpower source lines 126 c and 126 d. The third openings 180 and thefourth openings 182 each have a long, narrow opening shape along thedirection in which the data wirings 124 and the first power source lines126 extend. In other words, the first insulating layer 152 is providedwith third openings 180 and fourth openings 182 that are rectangular inshape along one side of the pixel electrode 162.

The pixel unit 106 shown in FIG. 9 is provided with the third insulatinglayer 160 over the data wiring 124 c and the first power source line 126a, as well as the source wiring 154 and the drain wiring 156, which areformed by the same layer as the data wiring 124 c and the first powersource line 126 a. As with the first insulating layer 152, the thirdinsulating layer 160 is made of an inorganic insulating material. Thethird insulating layer 160, for example, has a silicon nitride film or astructure in which a silicon nitride film and a silicon oxide film arestacked. As with the first insulating layer 152, such a third insulatinglayer 160 functions as a protective film for the transistors.

The third insulating layer 160 is provided with the third opening 180 bthrough which a part of the upper surface of the data wiring 124 b isexposed and the fourth opening 182 a through which a part of the uppersurface of the first power source line 126 a is exposed. That is, thethird insulating layer 160 has removed regions on the parts of the uppersurfaces of the data wiring 124 b and the first power source line 126 a.The third insulating layer 160 is provided in such a way as to cover theside surfaces and top edges of the data wiring 124 b and the first powersource line 126 a.

As with the first insulating layer 152, the third insulating layer 160,which is an inorganic insulating film, is brittle. Therefore, bendingthe first substrate 102 to a certain curvature or large undesirablycracks the third insulating layer 160. Meanwhile, the data wirings 124and the first power source lines 126 are formed by a metal film oftitanium, molybdenum, aluminum, or the like (e.g. a structure in whichan aluminum film is sandwiched between upper and lower titanium films)and, as such, have plasticity. Therefore, the data wirings 124 and thefirst power source lines 126 are not cracked even when the firstsubstrate 102 is bent, and have resistance to bending. The presentembodiment prevents the occurrence of cracks by being structured torelax the bending stress on the third insulating layer 160 by the thirdinsulating layer 160 having the third openings 180 and the fourthopenings 182 in regions that overlap the data wirings 124 and the firstpower source lines 126.

Furthermore, the third and fourth openings 180 and 182 provided in thethird insulating layer 160 are filled with the organic insulatingmaterial forming the second insulating layer 158. By filling, with theorganic insulating material forming the second insulating layer 158, theregions from which the third insulating layer 160 has been removed, thethird insulating layer 160 is prevented from being cracked when thefirst substrate 102 is bent. By thus being structured such that theinorganic insulating layer covering the data wirings and the powersource lines is provided with the openings and the openings are filledwith the organic insulating layer, the present embodiment allows thissite to function as a stress relaxation region.

In the present embodiment, by the openings (third openings 180, fourthopenings 182) being provided in the third insulating layer 160 in such away as to extend in a direction along the data wirings 124 (i.e. a Ydirection shown in FIG. 8), a display device can be provided whose firstsubstrate 102 is easily bent in a direction parallel to this directionby the action of the stress relaxation region.

Further, the openings provided in the third insulating layer 160 areformed to expose the parts of the upper surfaces of the data wirings 124and the first power source lines 126 and cover at least the sidesurfaces of the data wirings 124 and the first power source lines 126,thereby preventing the function of the third insulating layer 160 as aprotective film from being impaired. This allows the semiconductor layer142 a of the drive transistor 134 to have its upper surface covered withthe first insulating layer 152 and the sealing structure formed by thethird insulating layer 160, the data wirings 124, and the first powersource lines 126 and its lower surface covered with the foundationinsulating layer 140 and to be thereby protected from permeation ofimpurities such as moisture.

Thus, the present embodiment provides a display device that is easilybent in at least the direction in which the data wirings extend.Moreover, since the third insulating layer can be prevented from beingcracked even when the display device is bent, a decrease in reliabilitycan be prevented.

Third Embodiment

The present embodiment shows an example of a display device that can bebent along both gate wirings extending in a first direction and datawirings extending in a second direction intersecting the firstdirection.

FIG. 10 shows an aspect in which such pixels 116 as that shown in FIG. 4are arranged in the pixel unit 106. Further, FIG. 11 is across-sectional view of a pixel as taken along line A-B in FIG. 10. Thefollowing description refers to FIG. 10 and FIG. 11. It should be notedthat this line A-B corresponds to line A-B in the layout drawing of thepixel 116 shown in FIG. 4. The following describes parts that aredifferent from those of the structure shown in FIG. 6.

In the present embodiment, the pixel unit 106 shown in FIG. 10 isprovided with a first insulating layer 152 made of an inorganicinsulating material between the first gate wirings 120 a and 120 b andthe data wirings 124 a and 124 b, between the first gate wirings 120 aand 120 b and the first power source lines 126 a and 126 c, between thesecond gate wirings 122 a and 122 b and the data wirings 124 a and 124b, and between the second gate wirings 122 a and 122 b and the firstpower source lines 126 a and 126 c. Further, a third insulating layer160 is provided over the first insulating layer 152. Moreover, the firstinsulating layer 152 and the third insulating layer 160 are providedwith first openings 176 a to 176 f through which parts of the uppersurfaces of the first gate wirings 120 a, 120 b, and 120 c are exposed.Further, the first insulating layer 152 and the third insulating layer160 are provided with second openings 178 a to 178 f through which partsof the upper surfaces of the second gate wirings 122 a, 122 b, and 122 care exposed.

Furthermore, the third insulating layer 160 is provided with a thirdopening 180 a in a position that overlaps the data wiring 124 a, and isprovided with a fourth opening 182 a in a position that overlaps thefirst power source line 126 a. The third opening 180 a and the fourthopening 182 a extend in the directions in which the data wiring 124 aand the first power source lines 126 a extend, respectively. The sameform applies to the third openings 180 b and 180 c on the data wirings124 b and 124 c and the fourth openings 182 c and 182 d on the firstpower source lines 126 c and 126 d.

The configuration of the first opening 176 a and the second opening 178e in the first insulating layer 152 as well as the third opening 180 band the fourth opening 182 a in the third insulating layer 160 is thesame as those shown in the first and second embodiments. This makes itpossible to provide a display device that is easily bent in both a casewhere it is bent in a direction along the gate wirings and a case whereit is bent in a direction along the data wirings.

Fourth Embodiment

The present embodiment shows a configuration in which those portions ofthe first insulating layer 152 that were present on a lower level thanthe data wirings 124 and the first power source lines 126 are removedfrom the configuration of the third openings 180 on the data wirings 124and in the third insulating layer 160 and the configuration of thefourth openings 182 on the first power source lines 126 and in the thirdinsulating layer 160 in the second embodiment. The following describesparts that are different from those of the second embodiment withreference to FIG. 12 and FIG. 13. FIG. 12 is an arrangement plan ofpixels, and FIG. 13 is a cross-sectional view taken along line A-B.

Although not illustrated, the pixel unit 106 shown in FIG. 12 isprovided with a first insulating layer 152 and a third insulating layer160. The third insulating layer 160 is provided with third openings 180a to 180 c through which parts of the upper surfaces of the data wirings124 a to 124 c are exposed and fourth openings 182 a, 182 c, and 182 dthrough which parts of the upper surfaces of the first power sourcelines 126 are exposed. This configuration is the same as that describedin the second embodiment. On one hand, in the second embodiment, thoseportions of the first insulating layer 152 that are disposed on a lowerlevel than the data wirings 124 and the first power source lines 126remain. On the other hand, in the present embodiment, the firstinsulating layer 152 is provided with fifth openings 184 a 1 to 184 c 2in regions that overlap the data wirings 124 a to 124 c, and is providedwith sixth openings 186 a 1, 186 a 2, 186 c 1, 186 c 2, 186 d 1, and 186d 2 in regions that overlap the first power source lines 126 a, 126 c,and 126 d. The fifth openings 184 a 1 to 184 c 2 and the sixth openings186 a 1, 186 a 2, 186 c 1, 186 c 2, 186 d 1, and 186 d 2 are openingsthat penetrate the first insulating layer 152. It should be noted that,for insulation between wiring layers, the fifth openings 184 a 1 to 184c 2 and the sixth openings 186 a 1, 186 a 2, 186 c 1, 186 c 2, 186 d 1,and 186 d 2 are not provided in regions that intersect the first gatewirings 120 a to 120 c and the second gate wirings 122 a to 122 c,although the fifth openings 184 a 1 to 184 c 2 and the sixth openings186 a 1, 186 a 2, 186 c 1, 186 c 2, 186 d 1, and 186 d 2 are providedalong the direction in which the data wirings 124 a to 124 c and thefirst power source lines 126 a to 126 c extend.

Moreover, the fifth openings 184 a 1 to 184 c 2 correspond to firstmetal patterns 190 a 1 to 190 f 1 provided on a lower level than thefirst insulating layer 152. Further, the sixth openings 186 a 1 to 186 c2 correspond to second metal patterns 190 a 1 to 190 f 1. The datawirings 124 a to 124 c are in contact with the first metal patterns 190a 1 to 190 f 1 through the fifth openings 184 a 1 to 184 c 2,respectively. Further, the first power source lines 126 a, 126 c, and126 d are in contact with the second metal patterns 190 a 1, 190 a 2,190 b 1, 190 b 2, 190 c 1, 190 c 2, 190 d 1, 190 d 2, 190 e 1, 190 f 1,190 g 2, and 190 h 2 through the sixth openings 186 a 1, 186 a 2, 186 c1, 186 c 2, 186 d 1, and 186 d 2, respectively.

As shown in FIG. 13, the fifth opening 184 b 1 in the first insulatinglayer 152 is closed by the data wiring 124 b, which is on a higher levelthan the first insulating layer 152, being depressed into the firstmetal pattern 190 e 1, which is on a lower level than the firstinsulating layer 152. Similarly, the sixth opening 186 a 1 in the firstinsulating layer 152 is closed by the first power source line 126 a,which is on a higher level than the first insulating layer 152, beingdepressed into the second metal pattern 190 e 1, which is on a lowerlevel than the first insulating layer 152. Thus, although the firstinsulating layer 152 is provided with the fifth openings 184 and thesixth openings 186, the first insulating layer 152 keeps functioning asa protective film for the semiconductor layers 142, as the fifthopenings 184 are closed by the data wirings 124 and the first metalpatterns 190 and the sixth openings 186 are closed by the first powersource lines 126 and the second metal patterns 190.

The present embodiment allows stress relaxation regions to be providedalong the data wirings 124 by a structure in which the third openings180 and the fifth openings 184 are provided in the third insulatinglayer 160 and the first insulating layer 152, respectively, in such away as to overlap each other, in which the data wirings 124 are furtherprovided in these sites, and in which the first metal patterns 190 arefurther provided on a lower level than the data wirings 124. Further,the present embodiment allows stress relaxation regions to be providedalong the first power source lines 126 by a structure in which thefourth openings 182 and the sixth openings 186 are provided in the thirdinsulating layer 160 and the first insulating layer 152, respectively,in such a way as to overlap each other, in which the first power sourcelines 126 are further provided in these sites, and in which the secondmetal patterns 190 are further provided on a lower level than the firstpower source lines 126. This removes those portions of the firstinsulating layer 152 that are disposed on a lower level than the datawirings 124 and the first power source lines 126, thus achieving astress relaxation structure with increased resistance to the bending ofthe first substrate 102.

The present embodiment makes it possible to provide a display devicethat is easily bent in a direction along the data wirings 124 or thefirst power source lines 126. In this case, where the inorganicinsulating layer on a lower level than the data wirings 124 is partiallyremoved, the occurrence of cracks in the inorganic insulating layer canbe more effectively prevented.

It should be noted that although the present embodiment shows an aspectin which the first insulating layer 152 is provided with the fifthopenings 184 corresponding to the data wirings 124 and the sixthopenings 186 corresponding to the first power source lines 126, thepresent invention is not limited to this aspect. For example, similareffects can be brought about by providing the first insulating layer 152with a stress relaxation structure according to the present embodimentin either the data wirings 124 or the first power source lines 126.

Further, as with the third embodiment, the present embodiment allows thefirst insulating layer 152 to be further provided with first openings176 through which the upper surfaces of the first gate wirings 120 areexposed and second openings 178 through which the upper surfaces of thesecond gate wirings 122 are exposed. This makes it possible to provide adisplay device that is easily bent in both a case where the firstsubstrate 102 is bent in a direction along the gate wirings and a casewhere the first substrate 102 is bent in a direction along the datawirings.

Fifth Embodiment

The present embodiment exemplifies an example differing in the structureof wirings in each pixel 116 and the structure of openings through whichan inorganic insulating layer is exposed.

FIG. 14 shows an arrangement of the first transistor 130, the secondtransistor 132, the drive transistor 134, the light-emitting element136, the retentive capacitive element 138, the first gate wiring 120,the second gate wiring 122, the data wiring 124, and the first powersource line 126 in a pixel 116. The difference from the layout of thepixel shown in FIG. 4 lies in the structure of connection between thedrive transistor 134 and the second transistor 132.

In FIG. 14, the semiconductor layer 142 a of the drive transistor 134and the semiconductor layer 142 c of the second transistor 132 areprovided as one continuous island-shaped semiconductor region. Thesemiconductor layer 142 a of the drive transistor 134 and thesemiconductor layer 142 c of the second transistor 132 are coupled toeach other in a semiconductor region made lower in resistance by beingdoped with the same impurities as the drain region. For this reason,this semiconductor region has the same function as the drain wiring 156shown in FIG. 4.

FIG. 15 shows an aspect in which such pixels 116 as that shown in FIG.14 are arranged in the pixel unit 106. The following describes partsthat are different from those of the first embodiment with reference toFIG. 15 and FIG. 16. FIG. 15 is an arrangement plan of pixels, and FIG.16 is a cross-sectional view taken along line A-B.

FIG. 15 shows a first pixel 116 a, a second pixel 116 b, a third pixel116 c, and a fourth pixel 116 d, and in each of the pixels, seventhopenings 188 (seventh openings 188 a to 188 d) are provided throughwhich the aforementioned semiconductor region is exposed.

FIG. 16 shows a cross-sectional structure of the pixel 106, includingthe drive transistor 134 and the second transistor 132. Thesemiconductor layer 142 a of the drive transistor 134 and thesemiconductor layer 142 c of the second transistor 132 are continuouslyprovided. The doped semiconductor region linking the semiconductorlayers 142 a and 142 c together functions as a drain wiring 192. Whilethe gate insulating layer 146 and the first insulating layer 152 areprovided on a higher level than the semiconductor layers 142 a and 142c, those portions of the gate insulating layer 146 and the firstinsulating layer 152 that are on a higher level than the drain wiring192 formed by the semiconductor layer have been removed. That is, thegate insulating layer 146 is provided with a seventh opening 188 throughwhich the drain wiring 192 formed by the semiconductor layer is exposed.That is, the upper surface of the drain wiring 192 formed by thesemiconductor layer is exposed through the seventh opening 188. Theseventh opening 188 is filled with the organic insulating materialforming the second insulating layer 158 and functions as a stressrelaxation region in the same manner as that described in the firstembodiment.

Further, as shown in FIG. 17, the seventh opening 188 may be providedwith a metal wiring layer 194. This allows the seventh opening 188provided in the gate insulating layer 146 and the first insulating layer152 to be sealed with the metal wiring layer 194. That is, by providingthe metal wiring layer 194 that covers the seventh opening 188 formed inthe gate insulating layer 146 and the first insulating layer 152 and isin contact with the drain wiring 192 formed by the semiconductor layer,a sealed structure can be provided in which the semiconductor layersforming the transistors are covered with the inorganic insulating filmand the metal film. Further, by providing the seventh opening 188 withthe metal wiring layer 194, the drain wiring 192 formed by thesemiconductor layer can be made lower in resistance.

By thus providing, in a pixel region, a region from which the inorganicinsulating layer is removed, the inorganic insulating layer can beprevented from being cracked when the display device is bent, and theregion can be used as a stress relaxation region.

It should be noted that although FIG. 14 and FIG. 15 simultaneously showthe first openings 176 (176 a to 176 f) on the first gate wirings 120and the second openings 178 (178 a to 178 f) on the second gate wirings122, the present embodiment is not limited to this. Alternatively, byproviding the seventh openings 188 with only stress relaxation regionsonly in the pixels 116, the inorganic insulating layer can be preventedfrom being cracked when the display device is bent. Further, thecomponents of the present embodiment and the components of the first tofourth embodiments may be combined as appropriate for implementation.

Sixth Embodiment

Although the configuration of the pixel unit 106 shown in FIG. 6 showsthe top-gate structure of the drive transistor and a correspondingstructure of gate wirings and a data wiring, the present invention isnot limited to this. For example, the drive transistor may have areverse-staggered structure, with a corresponding structure of gatewirings and a data wiring.

FIG. 18 shows a configuration of a pixel unit 106 having arevere-staggered drive transistor 134. The gate electrode 148 a isprovided over the foundation insulating layer 140, and the gateinsulating layer 146 and the semiconductor layer 142 a are stacked on ahigher level than the gate electrode 148 a. The source wiring 154 andthe drain wiring 156 are provided in contact with the semiconductorlayer 142 a. It should be noted that a semiconductor layer 144, madelower in resistance, which corresponds to the source region and thedrain region, may be provided between the semiconductor layer 142 a andthe source wiring 154 and between the semiconductor layer 142 a and thedrain wiring 156. The first insulating layer 152 and the secondinsulating layer 158 are provided over the source wiring 154 and thedrain wiring 156. The configuration on a higher level than the secondinsulating layer 158 is the same as that shown in FIG. 6.

The first gate wiring 120 a and the second gate wiring 122 c are formedon a lower level than the gate insulating layer 146. Therefore, thefirst opening 176 a and the second opening 178 b are provided in such away as to penetrate the gate insulating layer 146 as well as the firstinsulating layer 152. The first opening 176 a and the second opening 178e are filled with the inorganic insulating layer forming the secondinsulating layer 158.

Further, the data wiring 124 b and the first power source line 126 a,which are formed by the same layer as the source wiring 154 and thedrain wiring 156, are covered with the first insulating layer 152. Onparts of the upper surfaces of the data wiring 124 b and the first powersource line 126 a, openings equivalent to a third opening 180 and afourth opening 182 may be provided.

Thus, as in the case of the first embodiment, by wirings disposed in apixel region, opening provided in an inorganic insulating layer coveringthese wirings, and an organic insulating layer filling these openings, astructure can be provided which prevents the occurrence of cracks in theinorganic insulating layer by relaxing the stress generated by bendingthe pixel unit 106.

Seventh Embodiment

The present embodiment exemplifies a structure that makes it possible tocontrol the direction in which a display device is bent, in addition toa stress relaxation structure according to any one of the first to fifthembodiments.

FIG. 20 shows the same component as the pixel unit 106 shown in thefirst embodiment, except that the second insulating layer 158 isprovided with a raised portion 196 that is larger in film thickness thanthe other region and that is provided in a region in the secondinsulating layer 158 that overlaps the first opening 176 a and thesecond opening 178 e. That is, although the second insulating layer 158has a flat region on which the pixel electrode 162 is provided, thesecond insulating layer 158 is provided with a raised portion 196 thatis larger in film thickness than the other regions and that is providedin a region outside the pixel electrode 162. The raised portion 196 ofthe second insulating layer 158 is provided in such a belt shape alongthe direction in which the first gate wirings 120 and the second gatewirings 122 extend as to overlap the first opening 176 a and the secondopening 178 e.

Such a raised portion 196 of the second insulating layer 158 acts tomake it harder for the display device 100 to be bent in a directionintersecting a direction parallel to the first gate wirings 120 and thesecond gate wirings 122 than in a case where it is bent in the directionparallel to the first gate wirings 120 and the second gate wirings 122.This makes it harder for one principal surface of the first substrate102 to be bent in such a direction as to become a concave surface thanin a case where the principal surface is bent into an outward convexsurface. Further, as shown in FIG. 19, when a stress relaxationstructure is provided along the first gate wirings 120 and the secondgate wirings 122, providing the raised portion 196 of the secondinsulating layer 158 along this stress relaxation structure makes itpossible to prevent the inorganic insulating layer such as the firstinsulating layer from being cracked when the display device 100 is bentin one direction.

FIG. 21 shows a configuration in which a depressed portion 200 that issmaller in film thickness than the other regions is provided in a regionin the second insulating layer 158 that overlaps the first and secondopenings 176 a and 178 e provided in the first insulating layer 152. Thedepressed portion 200 of the second insulating layer 158 is provided insuch a belt shape along the direction in which the first gate wirings120 and the second gate wirings 122 extend as to overlap the firstopening 176 a and the second opening 178 e.

By the second insulating layer 158 having the depressed portion 200, oneprincipal surface of the first substrate 102 is made easily bendable ina case where it is bent into an inward concave surface. In this case,providing a stress relaxation structure along the direction in which thedisplay device 100 is easily bent makes it possible to prevent theoccurrence of cracks in the inorganic insulating layer.

As shown in FIG. 19, a region between each of the pixels 116 and theother in the pixel unit 106 serves as a non-display region. By providingthe second insulating layer 158 with a raised portion 196 or a depressedportion 200 in this region, a structure can be provided which, whileretaining the flatness of the pixels 116, controls the direction inwhich the display device 100 bends.

The shape of a raised portion 196 or a depressed portion 200 on or inthe second insulating layer 158 can be formed by etching. For example,the surface of the second insulating layer 158 needs only be etched backso that a raised portion 196 or a depressed portion 200 is formed on orin the second insulating layer 158. Alternatively, a photosensitiveorganic resin material may be molded into the second insulating layer158 by a half-exposure technique so that a raised portion 196 or adepressed portion 200 is formed on or in the second insulating layer158.

Such regions, shown in the present embodiment, of the second insulatinglayer 158 where a raised portion 196 or a depressed portion 200 isprovided may be uniformly provided in the pixel unit 106 or may beprovided in particular regions. FIG. 22 shows an example of a displaydevice 100 in which, in the pixel unit 106, the second insulating layer158 is provided with a raised portion region 198 where a raised portion196 is provided and a depressed portion region 202 where a depressedportion 200 is provided. The display device 100 is bent so that thepixel unit 106 has an outward convex surface in the raised portionregion 198 and the pixel unit 106 has a depressed surface in thedepressed portion region 202. Further, between the raised portion region198 and the depressed portion region 202, a region may be provided wherethe second insulation layer 158 is not provided with a raised portion196 or a depressed portion 200.

By thus partially providing the raised portion region 198 and thedepressed portion region 202, easily bendable regions can be fabricatedinto the pixel unit 106, thus making it possible to provide a displaydevice 100 having a curved display screen.

FIG. 23 shows a case where a first substrate 102 a is formed by anorganic resin layer having a two-layer structure. The first substrate102 a includes a first resin layer 204 a, a second resin layer 204 b,and an inorganic insulating layer 206 a sandwiched between the firstresin layer 204 a and the second resin layer 204 b. Such a firstsubstrate 102 a is provided with a slit 208 a by making a part of thefirst substrate 102 a thinner in conformance with a region of the secondinsulating layer 158 that differs in film thickness. This allowspreferential bending of a region around the pixel electrode 162 whileminimizing bending of the part where the light-emitting element 136 isprovided. This makes it possible to minimize stress on the organic layer170 of the light-emitting element 136 and, for example, makes itpossible to prevent the organic layer 170 from being stripped from thepixel electrode 162.

The first substrate 102 a can be provided with the slit 208 a byremoving or processing the second resin layer 204 b so that the secondresin layer 204 b becomes thinner. For example, the second resin layer204 b can be removed by laser processing with the inorganic insulatinglayer 206 a as a border.

Further, FIG. 23 shows a second substrate 104 a placed opposite thefirst substrate 102 a. The second substrate 104 a includes a first resinlayer 204 c, a second resin layer 204 d, and an inorganic insulatinglayer 206 b sandwiched between the first resin layer 204 c and thesecond resin layer 204 d. Moreover, by providing, in a region thatoverlaps the slit 208 a of the first substrate 102 a, a slit 208 b fromwhich the second resin layer 204 d has been removed, the region aroundthe pixel electrode 162 can be made preferentially bendable.Furthermore, although the slit 208 a is provided, the first resin layer204 a is sandwiched between the foundation insulating layer 140 and theinorganic insulating layer 206 a. This prevents moisture or oxygen fromentering the first resin layer 204 a.

It should be noted that the first substrate 102 a and the secondsubstrate 104 a are not limited to such a two-layer structure, and evenin the case of a single-layer structure, a preferentially bendableregion can be similarly fabricated by providing slits 208.

According to the present embodiment, the direction in which the displaydevice 100 easily bends can be controlled by providing the secondinsulating layer 158 with a region that differs in film thickness. Acombination of such a configuration and a stress relaxation structureaccording to any one of the first to fifth embodiments makes it possibleto provide a display device that is easily bent in a predetermineddirection and, even when bent, can be prevented from deteriorating.

Eighth Embodiment

While the seventh embodiment discloses a structure in which the firstsubstrate 102 a varies in thickness from one part thereof to another,the present embodiment can make the display device 100 flexible byadding slits at a module level. FIG. 24 is a schematic view of across-sectional structure of a display device 100 provided with slits ata module level.

In FIG. 24, the foundation insulating layer 140 is provided over thefirst substrate 102 a, and a pixel circuit unit 1106 is provided on theupper surface of the foundation insulating layer 140. Light-emittingelements 136 a to 136 c are provided over the pixel circuit unit 1106.The second substrate 104 is provided on a higher level than thelight-emitting elements 136. An optical film 212 such as a circularlypolarizing plate, a touch panel 214, and a protective film 216 areprovided on a higher level than the second substrate 104.

Moreover, the first substrate 102 a (specifically, the resin layer 204b), a heat-diffusing plate 210, and a protective film 610 are providedwith slits 208 a and the protective film 216 is provided with slits 208b so that the slits 208 a and 208 b overlap a region in the pixelcircuit unit 1106 where a stress relaxation region is provided. Thisallows the module structure to ensure flexibility as a whole. Further,the protective film 216 may be similarly provided with the slits 208 bin positions that correspond to the slits 208 a in the first substrate102 a. These slits are disposed on the borders of a light-emittingelement 136 and a light-emitting element 136.

It should be noted that although FIG. 24 shows an aspect in which eachof the pixels 116 is provided with a slit, the present invention is notlimited to this aspect. For example, each block unit of pixels may beprovided with a slit. Further, slits may extend only in either thecolumn-wise or row-wise direction in which the pixels are arranged. Ineither case, it is preferable that slits that are provided at a modulelevel be provided in such a way as to overlap a stress relaxation regionthat is provided in the pixel unit 106.

Thus, by providing the heat-diffusing plate and the protective film withslits, the present embodiment can provide a display device havingflexibility at a module level. Furthermore, although the slits 208 a areprovided, the first resin layer 204 a is completely surrounded by thefoundation insulating layer 140 and the inorganic insulating layer 206.This prevents moisture or oxygen from entering the first resin layer 204a.

Ninth Embodiment

The present embodiment shows an example of a display device whosedisplay screen can be bent. FIG. 25 shows an example of a pixel unit 106according to the present embodiment, and FIG. 26 shows a cross-sectionalstructure taken along line A-B in FIG. 25. The following descriptionrefers to FIG. 25 and FIG. 26.

FIG. 25 shows a configuration of the pixel unit 106 in which the firstpixel 116 a, the second pixel 116 b, the third pixels 116 c, and thefourth pixel 116 d are arranged, with the superimposition of the banklayer 168 through which the pixel electrode of each of the pixels isexposed. In the present embodiment, the pixel unit 106 has a corrugatedregion 218 where the second insulating layer 158 has a wavy orcorrugated (or embossed) upper surface that overlaps the bank layer 168.In other words, the second insulating layer 158 has a wavy or corrugatedregion that overlaps the bank layer 168 and that includes a thick-filmregion and a thin-film region.

The wavy or corrugated region 218 in the second insulation layer 158 canbe provided one or more regions (including all of the regions) selectedfrom the following regions: a region that overlaps the first opening 176a and the second opening 178 e, a region that overlaps the third opening180 c and the fourth opening 182 d, and a region that overlaps the firstopening 176 to the fourth opening 182. By thus providing the secondinsulation layer 158 with the wavy or corrugated region 218 so that thewavy or corrugated region 218 overlaps openings provided in the firstinsulating layer 152, the first insulating layer 152 can be preventedfrom being cracked in a region where the first substrate 102 is bent.

According to the present embodiment, by providing the second insulatinglayer 158 with a wave shape or a corrugated shape, the surface of thefirst substrate 102 to which the pixel unit 106 is provided can be madeeasily bendable both inward and outward. In this case, a combination ofconfigurations according to the first to fifth embodiments makes itpossible to prevent the occurrence of cracks in the first insulatinglayer 152.

Tenth Embodiment

An embodiment of the present invention is not limited in terms of thearrangement of pixels 116 in the pixel unit 106. For example, as shownin FIG. 27, the pixels 116 (i.e. pixels 116 a to 116 j) may be arrangedin a honeycomb structure, and the gate wirings 120 and the data wirings124 may extend in a zigzag through spaces between pixels. In such apixel unit 106, by providing a stress relaxation region according to anyone of the first to fifth embodiments and applying a structure of thesecond insulating layer 158 according to the sixth or seventhembodiment, a structure can be applied in which the pixel unit 106 iseasily bent in any direction.

What is claimed is:
 1. A flexible display device comprising: a firstflexible substrate; and a plurality of pixels above the first flexiblesubstrate, each of the plurality of pixels includes: a first inorganicmaterial layer over the first flexible substrate; a first inorganicinsulation layer over the first inorganic material layer; a firstorganic insulation layer over the first inorganic insulation layer; andan organic light emitting element over the first organic insulationlayer, wherein the plurality of pixels are arranged in a matrix over thefirst flexile substrate, the first inorganic insulation layer has afirst opening exposing a part of a top surface of the first inorganicmaterial layer in each of the plurality of pixels, a first part of thefirst organic insulation layer is buried in the first opening in each ofthe pixels, and the first part of the first organic insulation layer isin contact with the part of the top surface of the first inorganicmaterial layer in the first opening.
 2. The flexible display deviceaccording to claim 1, wherein each of the plurality of pixels include afirst transistor and a first metal layer between the first inorganicinsulation layer and the first organic insulation layer, wherein thefirst inorganic material layer is a first semiconductor layer thatincludes a semiconductor wiring region, the first opening is arrangeddirectly above the semiconductor wiring region, and the first transistorincludes a portion of the first semiconductor layer outside the firstopening, a portion of the first inorganic insulation layer directlyabove the portion of the first semiconductor layer and a portion of thefirst metal layer directly above the portion of the first semiconductorlayer.
 3. The flexible display device according to claim 2, furthercomprising: a second inorganic insulation layer between the firstinorganic insulation layer and the first organic insulation layer; aplurality of data signal lines extending in a first direction andarranged in a second direction differing from the first direction; and aplurality of gate signal lines extending in the second direction andarranged in the first direction, wherein each of the plurality of pixelsis arranged between corresponding two of the date signal lines andcorresponding two of the gate signal lines, the data signal lines andthe gate signal lines are arranged between the second inorganicinsulation layer and the first inorganic insulation layer, the secondinorganic insulation layer has a second opening, the second opening isarranged directly above each of the date signal lines and extending inthe first direction, the second inorganic insulation layer has a thirdopening, the third opening is arranged directly above each of theplurality of gate signal lines and extending in the second direction, asecond part of the first organic insulation layer is buried in thesecond opening, a third part of the first organic insulation layer isburied in the third opening, the second part of the first organicinsulation layer is connected to a part of a top surface of each of theplurality of data signal lines in the second opening, and the third partof the first organic insulation layer is connected to a part of a topsurface of each of the plurality of gate signal lines in the thirdopening.
 4. The flexible display device according to claim 3, furthercomprising: a plurality of first metal lines directly below theplurality of data signal lines; and a third inorganic insulation layerbetween the second inorganic insulation layer and the first inorganicinsulation layer, wherein the plurality of data signal lines arearranged between the second inorganic insulation layer and the thirdinorganic insulation layer, the plurality of gate signal lines arearranged between the third inorganic insulation layer and the firstinorganic insulation layer, the third inorganic insulation layer has afourth opening, the fourth opening is arranged directly above each ofthe plurality of first metal lines and extending in the first direction,a part of each of the plurality of data signal lines is buried in thefourth opening and is connected to the each of the first metal lines. 5.The flexible display device according to claim 1, further comprising: asecond inorganic insulation layer between the first inorganic insulationlayer and the first organic insulation layer; a plurality of data signallines extending in a first direction and arranged in a second directiondiffering from the first direction; and a plurality of gate signal linesextending in the second direction and arranged in the first direction,wherein each of the plurality of pixels is arranged betweencorresponding two of the date signal lines and corresponding two of thegate signal lines, the plurality of data signal lines and the pluralityof gate signal lines are arranged between the second inorganicinsulation layer and the first inorganic insulation layer, the secondinorganic insulation layer has a second opening, the second opening isarranged directly above each of the plurality of date signal lines andextending in the first direction, the second inorganic insulation layerhas a third opening, the third opening is arranged directly above eachof the plurality of gate signal lines and extending in the seconddirection, a second part of the first organic insulation layer is buriedin the second opening, a third part of the first organic insulationlayer is buried in the third opening, the second part of the firstorganic insulation layer is connected to a part of a top surface of eachof the plurality of data signal lines in the second opening, and thethird part of the first organic insulation layer is connected to a partof a top surface of each of the plurality of gate signal lines in thethird opening.
 6. The flexible display device according to claim 5,further comprising: a plurality of first metal lines directly below thedata signal lines; and a third inorganic insulation layer between thesecond inorganic insulation layer and the first inorganic insulationlayer, wherein the plurality of data signal lines are arranged betweenthe second inorganic insulation layer and the third inorganic insulationlayer, the plurality of gate signal lines are arranged between the thirdinorganic insulation layer and the first inorganic insulation layer, thethird inorganic insulation layer has a fourth opening, the fourthopening is arranged directly above each of the plurality of first metallines and extending in the first direction, and a part of each of theplurality of data signal lines is buried in the fourth opening and isconnected to the each of the plurality of first metal lines.
 7. Theflexible display device according to claim 4, further comprising: asecond flexible substrate on the organic light emitting element; a firstprotection film under the first flexible substrate; and a secondprotection film on the second flexible substrate, wherein the firstprotection film includes a plurality of first grooves, the secondprotection film includes a plurality of second grooves, the firstgrooves extend in the second direction and are arranged in the firstdirection, and the second grooves extend in the second direction and arearranged in the first direction.
 8. The flexible display deviceaccording to claim 7, wherein the first flexible substrate includes afirst organic portion, a first inorganic portion on the first organicportion, and a second organic portion on the first inorganic portion,and the second flexible substrate includes a third organic portion, asecond inorganic portion on the third organic portion, and a fourthorganic portion on the second inorganic portion, wherein the firstorganic portion includes a plurality of third grooves, the fourthorganic portion includes a plurality of fourth grooves, the thirdgrooves extend in the second direction and are arranged in the firstdirection, and the fourth grooves extend in the second direction and arearranged in the first direction.
 9. A flexible display devicecomprising: a first flexible substrate; and a plurality of pixels abovethe first flexible substrate, each of the plurality of pixels includes:a first semiconductor layer over the first flexible substrate; a firstinorganic insulation layer over the first semiconductor; a first metallayer over the first inorganic insulation layer; a first organicinsulation layer over the first inorganic insulation layer and the firstmetal layer; and an organic light emitting element over the firstorganic insulation layer, wherein the plurality of pixels are arrangedin a matrix over the first flexile substrate, the first inorganicinsulation layer has a first opening exposing a part of a top surface ofthe first semiconductor in each of the plurality of pixels, a part ofthe first metal layer is buried in the first opening, a whole topsurface of the first metal layer is in contact with the first organicinsulation layer, and the first metal layer is not in contact with anyconductive material layer except for the first semiconductor layer. 10.The flexible display device according to claim 9, wherein each of theplurality of pixels include a first transistor, wherein the firstsemiconductor layer includes a semiconductor wiring region, the firstopening is arranged directly above the semiconductor wiring region, eachof the plurality of pixels includes a second metal layer between thefirst inorganic insulation layer and the first organic insulation layer,and the first transistor includes a portion of the first semiconductorlayer outside the first opening, a portion of the first inorganicinsulation layer directly above the portion of the first semiconductorlayer, and a portion of the second metal layer directly above theportion of the first semiconductor layer.
 11. The flexible displaydevice according to claim 10, further comprising: a second inorganicinsulation layer between the first inorganic insulation layer and thefirst organic insulation layer; a plurality of first signal linesextending in a first direction and arranged in a second directiondiffering from the first direction; and a plurality of second signallines extending in the second direction and arranged in the firstdirection, wherein each of the plurality of pixels is arranged betweencorresponding two of the first signal lines and corresponding two of thesecond signal lines, the plurality of first signal lines and theplurality of second signal lines are arranged between the secondinorganic insulation layer and the first inorganic insulation layer, thesecond inorganic insulation layer includes a second opening, the secondopening is arranged directly above each of the plurality of first signallines and extending in the first direction, a second part of the firstorganic insulation layer is buried in the second opening, and the secondpart of the first organic insulation layer is in contact with a part ofa top surface of each of the first signal lines in the second opening.12. The flexible display device according to claim 9, wherein each ofthe plurality of pixels include a first transistor, wherein the firstsemiconductor layer includes a semiconductor wiring region, the firstopening is arranged directly above the semiconductor wiring region, eachof the plurality of pixels includes a second metal layer between thefirst inorganic insulation layer and the first organic insulation layer,and the first transistor includes a portion of the first semiconductorlayer outside the first opening, a portion of the first inorganicinsulation layer directly above the portion of the first semiconductorlayer, and a portion of the second metal layer directly above theportion of the first semiconductor layer.
 13. The flexible displaydevice according to claim 9, further comprising: a second inorganicinsulation layer between the first inorganic insulation layer and thefirst organic insulation layer; a plurality of first signal linesextending in a first direction and arranged in a second directiondiffering from the first direction; and a plurality of second signallines extending in the second direction and arranged in the firstdirection, wherein each of the plurality of pixels is arranged betweencorresponding two of the first signal lines and corresponding two of thesecond signal lines, the plurality of first signal lines and theplurality of second signal lines are arranged between the secondinorganic insulation layer and the first inorganic insulation layer, thesecond inorganic insulation layer includes a second opening, the secondopening is arranged directly above each of the first signal lines andextending in the first direction, a second part of the first organicinsulation layer is buried in the second opening, the second part of thefirst organic insulation layer is in contact with a part of a topsurface of each of the first signal lines in the second opening.
 14. Theflexible display device according to claim 13, further comprising: aplurality of first metal lines extending in the first direction andarranged in the second direction; and a third inorganic insulation layerbetween the second inorganic insulation layer and the first inorganicinsulation layer, wherein the plurality of first signal lines arearranged between the second inorganic insulation layer and the thirdinorganic insulation layer, the third inorganic insulation layerincludes a third opening, the third opening is arranged directly beloweach of the plurality of first signal lines and extending in the firstdirection, and a part of each of the first metal lines is buried in thethird opening and is connected to the each of the first metal lines. 15.The flexible display device according to claim 11, further comprising: asecond flexible substrate over the organic light emitting element; afirst protection film under the first flexible substrate; and a secondprotection film over the second flexible substrate, wherein the firstprotection film includes a first groove, the second protection filmincludes a second groove, the first groove extends in the firstdirection, and the second groove extends in the first direction.
 16. Theflexible display device according to claim 15, wherein the firstflexible substrate includes a first organic portion, a first inorganicportion on the first organic portion, and a second organic portion onthe first inorganic portion, and the second flexible substrate includesa third organic portion, a second inorganic portion on the third organicportion, and a fourth organic portion on the second inorganic portion,wherein the first organic portion includes a third groove, the fourthorganic portion includes a fourth groove, the third groove extends inthe first direction, and the fourth groove extends in the firstdirection.
 17. The flexible display device according to claim 13,further comprising: a second flexible substrate over the organic lightemitting element; a first protection film under the first flexiblesubstrate; and a second protection film over the second flexiblesubstrate, wherein the first protection film includes a first groove,the second protection film includes a second groove, the first grooveextends in the first direction, and the second groove extends in thefirst direction.
 18. The flexible display device according to claim 17,wherein the first flexible substrate includes a first organic portion, afirst inorganic portion on the first organic portion, and a secondorganic portion on the first inorganic portion, and the second flexiblesubstrate includes a third organic portion, a second inorganic portionon the third organic portion, and a fourth organic portion on the secondinorganic portion, wherein the first organic portion includes a thirdgroove, the fourth organic portion includes a fourth groove, the thirdgroove extends in the first direction, and the fourth groove extends inthe first direction.